It is known that active noise cancellation (ANC) is a feature in audio headsets. Currently for most systems with ANC functions, the active circuitry is built into the headset along with a power source. The headset has a pair of microphones located close to each ear to sample the noise that is to be cancelled; those signals are processed in the headset and an anti-noise signal is generated. The anti-noise signal and the playback signal coming from the player are then the mixed and amplified to the earpiece.
The entire active headset is then connected to the audio device typically using a 3.5 mm jack. Cell phones, audio players and other headset devices generally use a 3.5 mM audio plug and socket for providing audio output to headphones or analogue interconnection with other audio devices. Headsets typically use a 3-connector system for stereo audio or mono audio and a microphone, and a 4-connector system for headsets with stereo output and a microphone input.
Alternatively, the ANC circuitry can be built into the audio processing device itself. This has the advantage of allowing the headset to operate without a battery and it reduces the cost of a headset. A problem with this approach is that is requires additional mechanical connections to pass the noise signals, from the headset to the audio device. Currently unique mechanical designs are used to enable those systems to be interoperable with standard headphones. However, this results in a system where only one side of the device/headset pair is compatible with standard equipment.
U.S. Pat. No. 7,270,554 uses additional mechanical connectors that are combined with a single standard stereo headphone connector. This enables a standard headset to be used with the audio device, but requires additional mechanical connectors for the ANC functions.
Sony uses a similar approach in its noise cancelling Walkman™ players by adding a unique mechanical connection on its headset, the receiving socket can be configured to allow for both the ANC version and standard headsets. However the Sony headset cannot be used with other audio players.
Therefore there is a need to develop a cheap audio headset that is compatible with standard connectors.